Effect of nitrogen-fixing bacteria on yield and some macronutrients of two barley cultivars

How to manage nitrogen consumption as one of the most important nutrients and challenges of its application in farms has been noticed by researchers. Due to low soil nitrogen content in the arid and semi-arid regions, as well as the adverse environmental effects of excessive use of nitrogen fertilizers, the role of nitrogen fixing-bacteria is very important. Some research has been done about how to use nitrogen fixing-bacteria and their effects on increasing the yield of various plants. The goal of this study was to investigate the role of nitrogen fixing-bacteria application (Azotobacter and Azospirillum) on the yield and concentration of some macro-nutrients in barley cultivars.

The experiment was conducted as factorial experiment in a completely randomized block design with three replications in research field of Agriculture College and Natural Resources of Darab, Shiraz University during 2017-2018 growing season. Experimental treatments included two barley cultivars (Zehak and Nimroz) and nitrogen source at six levels including control (no fertilizer applied), Azotobacter (Azotobacter chroococcum (seed inoculation alone, Azospirillum (Azospirillum lipoferum) seed inoculation alone, combination of Azotobacter with Azospirillum, combination of Azotobacter with Azospirillum with 100 kg/ha urea nitrogen source, and use of 200 kg urea nitrogen source alone. After harvesting manually, yield and yield components and the amount of nitrogen, phosphorus and potassium nutrients of seed were measured in the laboratory and data analyzed by SAS software.

The results showed that in Nimroz cultivar inoculation of seeds with each of Azotobacter and Azospirillum along with 100 kg urea application increased plant height and spike number per square meter by 9.74 and 18 % compared to control, respectively. Also, application of Azotobacter and Azospirillum with 100 kg urea 1000-kernel weight increased 18%. Increasing of 27.27% in biomass was observed in application of two bacteria together. The combination of Azotobacter and Azospirillum with 100 kg urea increased 40% and 21.33% grain yield of Zehak and Nimroz cultivars compared to control, respectively. Combined Azotobacter and Azospirillum with 100 kg urea treatment resulted in 21.6% increase in grain nitrogen content of barley. Seed inoculation of Zehak with Azospirillum and seed inoculation of Nimrooz with Azotobacter and Azospirillum together increased 9.58% and 30% of seed phosphorus compared to control, respectively. Finally, seed inoculation of Zehak with Azospirillum and seed inoculation of Nimrooz with Azotobacter and Azospirillum increased 42.58% and 61.74% of seed potassium.

The results of the present study showed that the use of nitrogen-fixing bacteria Azotobacter and Azospirillum with 100 kg urea decreased nitrogen fertilizer demand up to 50% and increased 1000- grain weight, nitrogen content and yield of barley.